NAtl_C1C2_photochem

Dissolved organic carbon (DOC) is one of Earth's major carbon reservoirs, but its sources and sinks remain poorly defined. Sunlight-induced photochemistry has long been postulated to be a DOC sink in the ocean, but its importance and impacts on marine DOC cycling, marine ecology, and atmospheric chemistry are far from resolved. This project aims to reduce this knowledge gap by addressing three key questions: 1) Are coastal-to-offshore acetone, pyruvate, and C1 and C2 compound photoproduction rates nonlinear functions of chromophoric dissolved organic matter (CDOM) absorption, as observed for DIC? 2) Is DIC the main carbon photoproduct produced from the photolysis of DOC in the open ocean? and 3) Is the production of C1 and C2 photoproducts, together with acetone and pyruvate, collectively a significant removal mechanism for DOC in the oceans on an annual basis? We will focus our study on C1 and C2 compounds because these are the main low molecular weight photoproducts that have been shown to be produced from the photolysis of marine DOC, and yet no one has co-measured these photoproducts in coastal or blue waters. Compounds that we will consider include CO, DIC, formaldehyde, acetaldehyde, formate, glyoxal, glyoxylate and possibly acetate. We will also quantify the C3 compounds acetone and pyruvate, since both have reported photochemical production rates in the low nM C h -1 range. To address the abovementioned questions, we propose a three-year study involving one 19-day research cruise in the Northwest Atlantic to study the photochemical production rates of the compounds listed above as well collect samples for subsequent photochemical experiments back in the home laboratory.